Muscles

Put the following stages of neuromuscular transmission into the correct temporal sequence

1. Ach diffuses across the cleft

2. voltage-gated Ca2_ channels in axon terminal open

3. generation of end-plate potential

4. reabsorption of choline by axon terminal

5. binding of Ach to receptors on sarcolemma

• 1,5,3,4,2

• 2,1,3,4,5

• 2,1,5,3,4

• 1,5,4,3,2

• 5,4,2,1,3

Which of the following statements about thick filaments is/are TRUE?

1. thick filaments are in the order of 12-18 nm in diameter

2. thick filaments are around 1.6 microns in length

3. each thick filament is made up of a large number of molecules of the protein myosin all packed togeher

• 2 & 3

• 2 only

• 1, 2 & 3

• 3 only

• 1 only

A number of muscle fibres collected together by a connective tissue sheath are known as which of the following?

• tendon

• motor unit

• sarcolemma

• fascicle

• fibula

The motor-end plate is the name given to which of the following?

• group of myofibrils immediately below the neuromuscular junction

• region where motoneurone axon terminal loses its myelin sheath

• cover that seals the drive shaft on a Holden Commodore

• part of neuromuscular junction that is closest to motoneurone soma

• region where motoneurone axon terminal and sarcolemma are in close apposition

Which of the following statements concerning the structure of a myofibril is/are TRUE?

1. the distance between the two bands is known as the sarcomere

2. the dark bands are caused by thin filaments and the light bands by the thick filaments

3. the Z line is caused by the junction between successive blocks of thick filaments

• 1 only

• 1, 2 & 3

• 1 & 2

• 2 & 3

• 2 only

Answer explanation

3. thin filaments

Which of the following statements about skeletal muscle is/are TRUE?

1. under the light microscope skeleta muscle appears striated

2. alternating dark and light bands are caused by highly ordered arrangement of thin and thick filaments within myofibril

3. dark bands known as I bands, light bands as A bands and thin line which is sometimes observed splitting I bands is known as Z lines

• 1, 2 & 3

• 2 & 3

• 1 & 2

• 2 only

• 1 only

Which of the following statements is/are TRUE?

1. thin filaments are in the order of 5-8 nm in diameter

2. thin filaments are around 1 micron long

3. thin filaments contain two chains of myosin which are twisted around each other to form a double helix

• 2 & 3

• 1 & 2

• 2 only

• 1 only

• 1, 2 & 3

Answer explanation

3. two chains of tropomyosin

If a muscle was found to have 90 muscle fibres innervated by each motoneurone, it would probably be involved in which of the following types of movement?

• stabilisation of the ear ossicles during hearing

• lower leg extension during kicking a football

• upper arm flexion while tossing the caber

• movement of the eyeball during reading

• movement of the thumb whilst writing

Which of the following structures are typically 1-2 microns thick?

• myofibrils

• transverse tubules

• muscle fibres

• thin myofilaments

• sarcolemma

An end-plate potential is the direct consequence of which of the following?

• flow of Na+ into the cell and K+ out of the cell

• opening of ligand-gated Ca2+ channels in motoneurone axon terminal

• flow of Na+ out of cell and K+ into cell

• binding of Ach to muscarinic Ach receptors